Cryptocurrency has always made a ripe target for theft—and not just hacking, but the old-fashioned, up-close-and-personal kind, too. Given that it can be irreversibly transferred in seconds with little more than a password, it's perhaps no surprise that thieves have occasionally sought to steal crypto in home-invasion burglaries and even kidnappings. But rarely do those thieves leave a trail of violence in their wake as disturbing as that of one recent, ruthless, and particularly prolific gang o...